1. Field of the Invention
The present invention relates in general to dentistry and, in particular, to a new and useful electrical device used in dentistry to remove tartar found on the teeth.
2. Background of the Invention
Similar devices are known, generally under the name of dental scalers, they facilitate the work of the dental practitioner and they are in current use in dentists' offices. These devices appear in the form of a cylindrical sleeve that can be held in the hand and comprising, at one extremity, a flexible electrical cable and, at the other extremity, a vibrating scraper. When the scraper is put in contact with the tartar, its rapid movements permit it to fissure the tartar and to detach it easily from the tooth on which it has been deposited.
In an embodiment that is marketed, the scraper is mounted on a vibrating piezoelectric transducer arranged inside the sleeve. The transducer comprises electrodes connected to the cable which, in turn, is connected to a source of alternating current supplying electric energy to the device. This alternating current is applied to the transducer and it has the effect of putting it into forced vibration. To obtain the best yield from the conversion of the electric energy supplied by the source into mechanical energy available at the extremity of the scraper, the current frequency must be equal to the fundamental resonant frequency of the transducer connected to the scraper, which is about 50 kHz. The amplitude of motion of the scraper is determined, in turn, by the amplitude of the voltage and, in order to be able to work under good conditions, this voltage should be on the order of 600 volts.
In use, such a device presents two principal disadvantages: The contact of the scraper with the tooth has the effect of modifying the resonant frequency of the transducer to which it is attached. Since the output of the transducer is reduced under these conditions, the voltage applied to the electrodes must be increased in order to keep the amplitude of the scraper constant. The thermal dissipation of the transducer can then become considerable and render the sleeve disagreeable to hold in one's hand.
Also, since the transducer has to be supplied with high tension current, about 600 volts, there is a risk of electrocution for both the patient and the physician, if the cable is badly insulated. To reduce this risk, the cable must have good insulation, to wit, a thick one. This has the effect of reducing the flexibility of the cable, rendering the movement of the sleeve difficult, yet without totally reducing the danger resulting from the wear and tear of the insulation in places where the cable is under greatest stress.